A New Ir‐NHC Catalyst for Signal Amplification by Reversible Exchange in D 2 O

NMR signal amplification by reversible exchange (SABRE) has been observed for pyridine, methyl nicotinate, N ‐methylnicotinamide, and nicotinamide in D 2 O with the new catalyst [Ir(Cl)(IDEG)(COD)] (IDEG=1,3‐bis(3,4,5‐tris(diethyleneglycol)benzyl)imidazole‐2‐ylidene). During the activation and hyperpolarization steps, exclusively D 2 O was used, resulting in the first fully biocompatible SABRE system. Hyperpolarized 1 H substrate signals were observed at 42.5 MHz upon pressurizing the solution with para hydrogen at close to the Earth's magnetic field, at concentrations yielding barely detectable thermal signals. Moreover, 42‐, 26‐, 22‐, and 9‐fold enhancements were observed for nicotinamide, pyridine, methyl nicotinate, and N ‐methylnicotinamide, respectively, in conventional 300 MHz studies. This research opens up new opportunities in a field in which SABRE has hitherto primarily been conducted in CD 3 OD. This system uses simple hardware, leaves the substrate unaltered, and shows that SABRE is potentially suitable for clinical purposes.